FIGS. 7 and 8 illustrate a conventional fuel supplying apparatus disclosed in International Publication No. W096/23967, FIG. 7 being a sectional side view and the FIG. 8 being a plan view. In these figures, it is seen that a cover 3 for closing an opening portion 2 of a fuel tank 1 has a fuel pump 4, a fuel filter 5, a pressure regulator 6, a fuel level gauge 7, an electric connector 8 and a discharge pipe 9 which are functional components of the fuel supply system assembled thereon as an integral unit. In the fuel tank 1 made of metal or synthetic resin, the opening portion 2 is formed. For closing the opening portion 2, the cover made of electrically insulating synthetic resin is provided. Between the cover 3 and the fuel tank 1 a gasket 10 is disposed on sealing therebetween.
The fuel filter 5 is composed of a filter element 12 made of paper accommodated within a housing 11. The cover 3 is one part of the housing 11 and the fuel filter 5 is suspended from the cover 3. The housing 11 comprises the cover 3 and the lower housing 13, which is electrically conducting because it is molded with a synthetic resin material in which an electrically conductive material such as carbon fibers or carbon powders is mixed. The cover 3 and the lower housing 13 are liquid-tightly welded together over the entire circumference at an interface portion 14 and the filter element 12 is inserted within the inner space.
At the upper inner circumference of the housing 11 of the fuel filter 5, an inlet pipe 5 as a fuel inlet is disposed and is connected to a discharge pipe 16 of the fuel pump 4. A pipe 17 (shown by dot-and-dash lines) defining a first fuel outlet out of the two fuel outlets of the housing 11 extends upwardly from the lower end of the lower housing 13 along the axial direction. The pipe 17 is communicated with the discharge pipe 9 disposed in the cover 3 to define a fuel passage 18 for supplying fuel filtered through the fuel filter 5 to the injectors for the engine. A return pipe 19 defining a second fuel outlet is disposed at the lower portion of the lower housing 13 and is connected to the pressure regulator 6.
The electrical connector 8 shown in FIG. 8 is molded integrally with the cover 3 by directly insert-molding a plurality of terminal pins 8a within the electrically insulating resin material of the cover 3. The terminal pins 8a of the electrical connector 8 are connected at the outside of the fuel tank 1 to an electric source and a control unit (not shown). Also, within the fuel tank 1 shown in FIG. 7, they are connected through unillustrated lead wires to an electrical connector portion 20 of the fuel pump 4 for supplying electric power to the motor of the fuel pump 4 and also connected through unillustrated lead wires to the fuel level gauge 7 (shown in FIG. 8) for transmitting an electric signal indicative of the fuel level.
In the fuel supplying apparatus having the above-described structure, when an electric power is supplied to the fuel pump 4 through the electrical connector 8 and the electrical connector portion 20, the fuel pump 4 sucks the fuel through the filter 21 to discharge it from the discharge pipe 16. The fuel flows through a flow path 22 defined between the lower housing 13 and the cover 3 in the direction shown by an arrow A. The fuel then flows through the housing 11 from top to bottom and while doing so the fuel flows through the filter element 12 to be filtered with respect to dust or the like. As for the fuel passed through the filter element 12 and arrived at a bottom space 23 of the housing 11, one portion of it is returned to the fuel tank 1 by the pressure regulator 6 to regulate the pressure of the fuel and the remaining major portion of the fuel is supplied through the discharge pipe 9 to the injectors (not shown) of the fuel injection apparatus mounted to the engine.
During the passage of the fuel through the filter element 12 made of paper, electrostatic electricity is generated due to the friction between the fuel and the filter element 12. This electricity is dissipated from the lower housing 13 made of an electrically conductive resin through water within the fuel to the exterior of the fuel tank 1.
In the conventional fuel supplying apparatus as above described, the electrostatic electricity generated by the friction between the fuel and the filter element 12 during the passage of the fuel through the paper filter element 12 is dissipated from the lower housing 13 made of an electrically conductive resin. However, with this structure, a contact between the lower housing 13 and the fuel tank 1 during the dismounting of the fuel filter 5 may cause a sparking electric discharge therebetween. This sparking electric discharge causes the lower housing 13 to deteriorate, generating fuel leakage through the deteriorated portion from the interior of the lower housing 13 to the interior of the fuel tank 1, degrading the filtering ability of the fuel filter 5 and decreasing the pressure of the fuel to an extent that the pressurized fuel cannot be supplied.